Cytotoxic T Lymphocytes (CTLs)

Definition

Cytotoxic T lymphocytes, also known as CD8+ T cells, are a type of T cell that play a crucial role in the adaptive immune response by directly killing infected or cancerous cells. They are a key component of cell-mediated immunity, functioning as the 'attack dogs' of the immune system.

5 Must Know Facts For Your Next Test

1. Cytotoxic T lymphocytes (CTLs) recognize and destroy cells that display foreign or abnormal peptide fragments on their surface, such as those infected with viruses or transformed into cancer cells.
2. CTLs use specialized cytotoxic granules containing perforin and granzymes to induce apoptosis, or programmed cell death, in target cells.
3. The activation and proliferation of CTLs is dependent on recognition of antigen-MHC class I complexes presented by infected or cancerous cells.
4. CTLs play a critical role in the body's defense against viral infections, as they can directly kill virus-infected cells and prevent the spread of the virus.
5. Impairment or dysfunction of CTLs can lead to the development of autoimmune diseases or the inability to effectively eliminate cancer cells.

Review Questions

• Explain the role of cytotoxic T lymphocytes (CTLs) in the context of transplantation immunology.
  • In the context of transplantation immunology, CTLs play a crucial role in the rejection of transplanted organs or tissues. When a foreign organ or tissue is transplanted, the recipient's immune system recognizes the transplant as 'non-self' and mounts an immune response. CTLs are a key effector cell in this process, as they can directly recognize and destroy the transplanted cells that display foreign MHC class I molecules. The activation and proliferation of CTLs is a major contributor to acute and chronic rejection of transplanted organs, which is a significant challenge in the field of transplantation medicine.
• Describe how cytotoxic T lymphocytes (CTLs) are involved in the body's immune response to cancer.
  • Cytotoxic T lymphocytes (CTLs) are a critical component of the body's immune defense against cancer. Cancer cells often display altered or mutated proteins on their surface, which can be recognized as 'non-self' by the immune system. CTLs can identify these cancer-specific antigens presented on MHC class I molecules and initiate the destruction of the cancerous cells through the release of cytotoxic granules containing perforin and granzymes. The ability of CTLs to selectively target and eliminate transformed, malignant cells makes them a key player in the body's natural anti-cancer immune response. Impairment or evasion of CTL-mediated killing is a common mechanism by which cancer cells can evade the immune system and continue to proliferate.
• Evaluate the potential therapeutic applications of harnessing cytotoxic T lymphocytes (CTLs) in the treatment of disease.
  • The potent cytotoxic capabilities of CTLs have led to the development of various immunotherapeutic approaches aimed at harnessing their power to treat disease. In the context of cancer, strategies such as adoptive cell transfer, where a patient's own CTLs are isolated, expanded, and reinfused, have shown promise in enhancing the body's anti-tumor immune response. Additionally, the use of checkpoint inhibitors to reinvigorate exhausted or suppressed CTLs has emerged as an effective cancer treatment. Beyond oncology, the ability of CTLs to recognize and eliminate infected cells has led to investigations into their potential role in combating viral infections, autoimmune disorders, and even transplant rejection. As our understanding of CTL biology and function continues to evolve, the therapeutic applications of these powerful immune cells are likely to expand, offering new avenues for the treatment of a wide range of diseases.

Related terms

T Cells: A type of lymphocyte that originates in the thymus and is responsible for cell-mediated immunity, recognizing and destroying infected or cancerous cells.

Major Histocompatibility Complex (MHC): A group of genes that encode cell surface proteins involved in the presentation of foreign antigens to T cells, allowing the immune system to recognize and respond to threats.

Apoptosis: Programmed cell death, a process by which infected or damaged cells are systematically broken down and removed from the body, often triggered by CTLs.